The present invention relates to a plugging device for the tap hole of a shaft furnace, particularly a blast furnace.
It is known how to plug the tap hole of a shaft furnace by injecting tap-hole clay. A known plugging device for injecting the tap-hole clay comprises a plugging chamber receiving the tap-hole clay, a piston fitted in the plugging chamber for the expulsion of the tap-hole clay and a powerful double-acting hydraulic actuator positioned along the axis of the expulsion piston. This hydraulic actuator is a double-acting actuator which is used to move the expulsion piston axially in the plugging chamber, either to inject the tap-hole clay through a plugging nose-piece under high pressure into the tap hole, or to bring back the expulsion piston into a rear position in the plugging chamber in order to be able to fill the plugging chamber with the tap-hole clay. This plugging device is supported by a supporting structure which makes it possible to move the plugging device from a parked position, at a distance from the tap hole, into a plugging position, in which the plugging nose-piece is firmly applied against the wall of the shaft furnace along the axial alignment of the tap hole.
A process for opening the tap hole is also known in which, after having blocked the tap hole with tap-hole clay, a metallic piercing rod is driven into the clay, before it completely hardens, and in which the said rod is extracted, after the tap-hole clay has completely hardened, in order to form and open a flow channel in the tap hole. This process of opening the tap hole is generally known as "the soaking rod process" or "the embedded rod process".
For the application of this "embedded rod process", it is known how to use, alongside the plugging device described above, special drilling machines comprising a carriage to support the piercing rod, a structure for supporting the carriage designed to be able to move the carriage from a parked position at a distance from the tap hole into a operating position in which the carriage is positioned along the extension of the axis of the tap hole, a driving mechanism installed on the carriage in such a way as to develop a tractive force or pushing force parallel to the longitudinal axis of the carriage and a coupling mechanism connected to this driving mechanism so as to be able to transmit the tractive and/or pushing force axially to the piercing rod.
In order to apply the "embedded rod process", the plugging device is first brought into its plugging position and the tap-hole clay is injected into the tap hole in order to block the tap-hole. After having brought the plugging device back into its parked position, the drilling machine is aligned along the axis of the tap hole and, without wasting any time, a piercing rod is driven into the tap-hole clay which is in the process of hardening in the tap hole.
From the French patent application FR-A-2.680.179, published Feb. 12, 1993 and the entire disclosure of which is incorporated herein by reference, a device for the injection of the tap-hole clay into the tap hole of a blast furnace is known. This device makes it possible to introduce a piercing rod into the tap hole simultaneously with the tap-hole clay. For this purpose, the expulsion piston for the tap-hole clay and the hydraulic actuator driving it are equipped with an axial channel for the passage of the piercing rod. Positioned behind the actuator driving the expulsion piston, for this purpose, is a system for driving the piercing rod comprising a grooved or notched roller moved by a rotary motor, one or more guide wheels and a push rod driven by the motorized roller and guided by the guide rollers. This driving system would make it possible, according to the document FR-A-2.680.179, to push a piercing rod, previously introduced into the axial channel of the plugging device, into the tap hole simultaneously with the tap-hole clay.
It is important to note that the known plugging device of the document FR-A-2.680.179 does not enable the tap-hole clay to be injected into the tap hole first and a piercing rod then to be introduced into previously injected tap-hole clay. In fact, the tap-hole clay, in the process of hardening in the tap hole, opposes the piercing rod with such a great resistance to its advancement that the motorized push-rod/grooved-roller driving system can no longer overcome it.